Object scala.util.control.Exception
object Exception
Type Members
class By[T, R] extends AnyRef
class Catch[+T] extends Described
A container class for catch/finally logic.
Pass a different value for rethrow if you want to probably unwisely allow catching control exceptions and other throwables which the rest of the world may expect to get through.
- T
result type of bodies used in try and catch blocks
type Catcher[+T] = PartialFunction[Throwable, T]
trait Described extends AnyRef
class Finally extends Described
Value Members
final def !=(arg0: Any): Boolean
Test two objects for inequality.
- returns
trueif !(this == that), false otherwise.
- Definition Classes
- AnyRef → Any
final def ##(): Int
Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.
- returns
a hash value consistent with ==
- Definition Classes
- AnyRef → Any
final def ==(arg0: Any): Boolean
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
- returns
trueif the receiver object is equivalent to the argument;falseotherwise.
- Definition Classes
- AnyRef → Any
final def allCatch[T]: Catch[T]
final def allCatcher[T]: Catcher[T]
final def asInstanceOf[T0]: T0
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
- returns
the receiver object.
- Definition Classes
- Any
- Exceptions thrown
ClassCastExceptionif the receiver object is not an instance of the erasure of typeT0.
def catching[T](c: Catcher[T]): Catch[T]
def catching[T](exceptions: Class[_]*): Catch[T]
Creates a Catch object which will catch any of the supplied exceptions. Since the returned Catch object has no specific logic defined and will simply rethrow the exceptions it catches, you will typically want to call opt, either or withTry on the return value, or assign custom logic by calling "withApply".
Note that Catch objects automatically rethrow ControlExceptions and others which should only be caught in exceptional circumstances. If you really want to catch exactly what you specify, use catchingPromiscuously instead.
def catchingPromiscuously[T](c: Catcher[T]): Catch[T]
def catchingPromiscuously[T](exceptions: Class[_]*): Catch[T]
Creates a Catch object which will catch any of the supplied exceptions. Unlike "catching" which filters out those in shouldRethrow, this one will catch whatever you ask of it including ControlThrowable or InterruptedException .
def clone(): AnyRef
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
- returns
a copy of the receiver object.
final def eq(arg0: AnyRef): Boolean
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:
-
It is consistent: for any non-null instances
x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
- returns
trueif the argument is a reference to the receiver object;falseotherwise.
- Definition Classes
- AnyRef
def equals(arg0: Any): Boolean
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
- returns
trueif the receiver object is equivalent to the argument;falseotherwise.
- Definition Classes
- AnyRef → Any
def failAsValue[T](exceptions: Class[_]*)(value: ⇒ T): Catch[T]
def failing[T](exceptions: Class[_]*): Catch[Option[T]]
def finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
- Note
not specified by SLS as a member of AnyRef
final def getClass(): Class[_]
Returns the runtime class representation of the object.
- returns
a class object corresponding to the runtime type of the receiver.
def handling[T](exceptions: Class[_]*): By[(Throwable) ⇒ T, Catch[T]]
Returns a partially constructed Catch object, which you must give an exception handler function as an argument to by.
handling(classOf[MalformedURLException], classOf[NullPointerException]) by (_.printStackTrace)
def hashCode(): Int
The hashCode method for reference types. See hashCode in scala.Any.
- returns
the hash code value for this object.
def ignoring(exceptions: Class[_]*): Catch[Unit]
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
- returns
trueif the receiver object is an instance of erasure of typeT0;falseotherwise.
- Definition Classes
- Any
def mkCatcher[Ex <: Throwable, T](isDef: (Ex) ⇒ Boolean, f: (Ex) ⇒ T)(implicit arg0: ClassTag[Ex]): Catcher[T]
def mkThrowableCatcher[T](isDef: (Throwable) ⇒ Boolean, f: (Throwable) ⇒ T): Catcher[T]
final def ne(arg0: AnyRef): Boolean
Equivalent to !(this eq that).
- returns
trueif the argument is not a reference to the receiver object;falseotherwise.
- Definition Classes
- AnyRef
final val noCatch: Catch[Nothing]
final def nonFatalCatch[T]: Catch[T]
final def nonFatalCatcher[T]: Catcher[T]
final val nothingCatcher: Catcher[Nothing]
final def notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
final def notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
- Definition Classes
- AnyRef
- Annotations
- @native()
- Note
not specified by SLS as a member of AnyRef
def shouldRethrow(x: Throwable): Boolean
!!! Not at all sure of every factor which goes into this, and/or whether we need multiple standard variations.
- returns
true if
xisControlThrowableorInterruptedExceptionotherwise false.
final def synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
implicit def throwableSubtypeToCatcher[Ex <: Throwable, T](pf: PartialFunction[Ex, T])(implicit arg0: ClassTag[Ex]): Catcher[T]
def toString(): String
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
- returns
a String representation of the object.
- Definition Classes
- AnyRef → Any
def ultimately[T](body: ⇒ Unit): Catch[T]
def unwrapping[T](exceptions: Class[_]*): Catch[T]
final def wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
final def wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
final def wait(arg0: Long): Unit
© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.12.9/scala/util/control/Exception$.html
Classes representing the components of exception handling.
Each class is independently composable.
This class differs from scala.util.Try in that it focuses on composing exception handlers rather than composing behavior. All behavior should be composed first and fed to a Catch object using one of the
opt,eitherorwithTrymethods. Taken together the classes provide a DSL for composing catch and finally behaviors.Examples
Create a
Catchwhich handles specified exceptions.import scala.util.control.Exception._ import java.net._ val s = "http://www.scala-lang.org/" // Some(http://www.scala-lang.org/) val x1: Option[URL] = catching(classOf[MalformedURLException]) opt new URL(s) // Right(http://www.scala-lang.org/) val x2: Either[Throwable,URL] = catching(classOf[MalformedURLException], classOf[NullPointerException]) either new URL(s) // Success(http://www.scala-lang.org/) val x3: Try[URL] = catching(classOf[MalformedURLException], classOf[NullPointerException]) withTry new URL(s) val defaultUrl = new URL("http://example.com") // URL(http://example.com) because htt/xx throws MalformedURLException val x4: URL = failAsValue(classOf[MalformedURLException])(defaultUrl)(new URL("htt/xx"))Create a
Catchwhich logs exceptions usinghandlingandby.def log(t: Throwable): Unit = t.printStackTrace val withThrowableLogging: Catch[Unit] = handling(classOf[MalformedURLException]) by (log) def printUrl(url: String) : Unit = { val con = new URL(url) openConnection() val source = scala.io.Source.fromInputStream(con.getInputStream()) source.getLines.foreach(println) } val badUrl = "htt/xx" // Prints stacktrace, // java.net.MalformedURLException: no protocol: htt/xx // at java.net.URL.<init>(URL.java:586) withThrowableLogging { printUrl(badUrl) } val goodUrl = "http://www.scala-lang.org/" // Prints page content, // <!DOCTYPE html> // <html> withThrowableLogging { printUrl(goodUrl) }Use
unwrappingto create aCatchthat unwraps exceptions before rethrowing.Use
failAsValueto provide a default when a specified exception is caught.Compose multiple
Catchs withorto build aCatchthat provides default values varied by exception.val formatDefaulting: Catch[Int] = failAsValue(classOf[NumberFormatException])(0) val nullDefaulting: Catch[Int] = failAsValue(classOf[NullPointerException])(-1) val otherDefaulting: Catch[Int] = nonFatalCatch withApply(_ => -100) val combinedDefaulting: Catch[Int] = formatDefaulting or nullDefaulting or otherDefaulting def p(s: String): Int = s.length * s.toInt // Int = 0 combinedDefaulting(p("tenty-nine")) // Int = -1 combinedDefaulting(p(null: String)) // Int = -100 combinedDefaulting(throw new IllegalStateException) // Int = 22 combinedDefaulting(p("11"))